The present invention relates generally to an apparatus and method for mounting sheet material to a support structure and, more particularly, to an apparatus and method for assembling the components of a window covering system, such as a Roman shade window covering system.
The prior art contains various devices for mounting, lifting, and folding flexible sheet material in association with blinds, curtains, draperies, and other window coverings. Some of these window shade devices include guide cables and lift cords in conjunction with a fabric-gripping device. These cables/cords are typically threaded through rings sewn to the shade fabric. Alternatively, the cables/cords are threaded through apertures in the fabric pleats, wherein the pleats may be formed or stiffened with slats. The lattice formed by the attachment of the shade fabric to these guide cables and lift cords constitutes a mobile support structure which allows the shade to travel between raised and lowered positions.
Roman shades are a particular type of window covering which incorporates a mobile support structure such as a lattice for gathering sheet fabric into substantially horizontal folds. One example of the construction of a contemporary Roman shade is a cloth fabric hanging from a head rail, with a lower end having weights at predetermined lateral intervals. Drawing up a lift cord can raise this type of Roman shade such that large, loose folds in the fabric are formed at approximately equal vertical distances to provide a neatly pleated aesthetic appearance. A common configuration for connecting the cord to the shade is to sew at least two sets of rings or connectors in vertical lines along the back of the fabric material as shown in U.S. Pat. No. 1,321,800 entitled CURTAIN HANGER issued to Andress, et al. on Nov. 18, 1919. In this type of Roman shade, a lift cord passes from a head rail through each set of rings and is then either fastened to the bottom edge of the fabric or wrapped around the bottom edge of the fabric and returned up the front face of the shade to the head rail. Alternatively, each set of rings or connectors is sewn to the sheet fabric and attached to a lift cord at predetermined vertical intervals. As the shade travels through raised positions, the interval between the connectors may be reduced.
However, due to the extensive time and labor to sew connectors to the back of the sheet material of a Roman shade, the art has developed other methods and devices to connect sheet fabric to a mobile support structure. In the shade system disclosed in U.S. Pat. No. 4,694,545 entitled ATTACHMENT OF RINGS WITHOUT SEWING issued to Dernis on Sep. 22, 1987, a set of U-shaped filaments is inserted through the fabric from the front face. The ends of each filament are gathered in a tube, bent over the end of the tube and held in place by a sleeve that fits over the tube.
Another alternative for attachment includes one or more horizontal ribs to provide support and to maintain spacing between the cords which are oriented vertically across the back of the fabric. For example, in U.S. Pat. No. 5,207,256 entitled SAFETY DEVICE FOR A RAISABLE CURTAIN DOOR issued to Kraeutler on May 4, 1993, the ribs are placed in vertically spaced, transverse pockets in the sheet material. However, in this system, the pockets must be sewn into the sheet material, thereby substantially adding to the time, effort, and expense of manufacture.
U.S. Pat. No. 5,273,096, entitled APPARATUS FOR GRIPPING SHEET FABRIC issued to Thomsen et al. on Dec. 28, 1993, discloses a tubular member having a longitudinal opening which receives the fabric and a rod, thereby gripping the fabric between the member and the rod. The backsides of the tubular members each include loops through which the lift cords pass. However, as shown in FIG. 10, if this system is used on a Roman shade for a large window, the combined weight of the tubular member and the rod will often cause tilting of the mounting device, thereby adding substantial friction to the lift cord and making it more difficult to raise the shade. More particularly, the fabric mounting device found in Thomsen et al. and other Roman shade systems employ designs wherein the center of gravity of the fabric mounting device causes the device to tilt asymmetrically as the shade is raised, distorting the fabric being held and thereby adding friction to the lift cord. Thus, the size of a Roman shade is often limited by the friction incident upon the lift cord caused by the tilting of one or more of the rings, connectors, loops, or spacers used to mount the fabric to the lift cord.
Several prior art methods purport to provide a system for uniformly raising a window shade, such as a Roman shade, thereby eliminating the tilting affect and increased friction on the lifting cords. One such prior art method, uses an angled off-set of a pair of lift cords to ensure that the lift cords may be raised without substantial cord overlapping. In particular, the method involves attaching the cord pair to a leveling rod positioned at the shade bottom. The cords are affixed equidistant from the opposing ends of the leveling rod. That is, when measured from the right and left borders of the shade, the left lift cord is affixed to the leveling rod at a distance, X, when measured from the left border, and the right lift cord is affixed to the leveling rod at a distance X, when measured from the right border. The tops of the cords are attached to a winding tube positioned at the upper most portion of the shade material. In this instance, the left lift cord is affixed at a distance, X-Y, from the left border, and the right cord is affixed at a distance, X-Y, from the right border. Thus, the line drawn by the left (and alternatively, the right) cord forms an angle with the winding tube. In this configuration, the prior art system purports to provide a method for raising the shade uniformly, since the cords will not be permitted to roll over each other during the raising and lowering of the shade. However, this method is not suitable for shades which require the lifting cords to be perpendicular to the lift tube during operation.
Another prior art system for lifting a shade with two lift cords involves using a traversing lifting tube in combination with lift cords which move relatively perpendicular to the lifting tube during operation. In this instance, at the top and bottom of the shade material, the left lift cord is affixed equidistant from left border, and the right lift cord is affixed equidistant from the right border. The lift cords are preventing from rolling over each other by the traversing motion of the winding tube. That is, as the winding tube is raised (or lowered) during operation of the system, the winding rod not only rotates to lift the cords, but also traverses in a left (or right) horizontal direction to ensure that the lift cords do not overlap during the winding process. When unwinding, the lift tube traverses in the opposite direction. However, this method is not suitable for shades which operate in a confined area. In particular, additional room is need for the traversal of the winding tube, preventing the use of this system within a narrow shade mounting area.
Yet another prior art system uses a segmented lift cone design in its winding mechanism. U.S. Pat. No. 5,328,113 issued Jul. 12, 1994 to Villette, and assigned to Somfy is exemplary of this design. The circumference of the outer lift cone is greater at the point where the lift cone is nearest the wall, and becomes narrower in the direction toward the shade material. Key to this design is the segmented characteristic of the lift cone. That is, the lift cone can be seen as multiple cones where the portion of each cone with the greatest outer circumference is joined to the portion of the preceding cone with the least outer circumference. In this configuration, where the cones are joined, there is a pronounced drop-off from the first cone to the subsequent cone. The drop-off purports to reduce the friction on the lift cords as the cords are wound, since the cords become wound around progressively narrower cone structures.
However, the Somfy cone poses some challenges. For example, the cone is expensive to produce since the overall structure involves joining several facets into a single cone structure. Further, the design of the cone structure with particular drop offs from cone to cone provides room for error. That is, where the cones are joined at an improper angle, the cone system would be deviated from its original design, and, thus, made less effective.
A need exists for a lightweight, sheet-material gripping apparatus which can be quickly assembled by the manufacturer and which includes both lightweight and inexpensive spacers that can be connected to the sheet material without sewing. Moreover, the gripping apparatus components should reduce the lift cord friction which often increases asymmetric tilting of the sheet-material connectors as the apparatus is raised. Additionally, there is a need for an apparatus and method for easily and rapidly assembling tightly fitted components of a sheet material gripping apparatus such that, once assembled, the components of each sheet material gripping apparatus are capable of maintaining vertical alignment with respect to other sheet material gripping apparatus comprised by the window covering system. Moreover, there is a need for an apparatus and method for easily adjusting and re-aligning assembled components of a sheet material gripping apparatus. Further still, there is a need for a sheet material winding structure which is inexpensive and which enables the operator to lift two or more lift cords while keeping the sheet material absolutely uniform as the sheet material is raised an lowered.
The present invention provides a sheet material mounting device having two channels, namely, a mounting channel for receivably engaging a rod for gripping the sheet material and a spacer channel for receivably engaging a spacer support configured to engage a lift cord and, optionally, a spacer cord. The spacer channel may be positioned above the mounting channel such that the center of gravity of the mounting device is located above the center of the mounting channel, thereby reducing asymmetric tilt of the sheet material engaged by the mounting channel and reducing function against the lift cord. Alternatively, the mounting channel may be positioned above the spacer channel. The mounting channel and the spacer channel are preferably both C-shaped, and each channel has an opening which faces in a direction opposite the direction faced by the opening of the other channel. Thus, a side view of the mounting device may resemble either an xe2x80x9cSxe2x80x9d or a reverse xe2x80x9cS.xe2x80x9d The lifting cord is attached to a cylindrical lifting sleeve for use in raising and lowering the shade sheet material. The outer surface of the cylindrical lifting sleeve is concave such that the arc formed by the outer surface represents a circular segment. As the sheet material is raised, the cord wraps around the lifting sleeve and traverses the sleeve from the distal end to the proximal end, facilitating the winding of the cord while minimizing or eliminating any cord stacking or overlap. This, in turn, provides a uniform and level lifting means of the fabric bands, with two or more lift sleeve and cord assemblies.
In accordance with another aspect of the invention, there is provided an apparatus and method for assembling the components of a sheet-material mounting device, such that the assembled components of each sheet material mounting device are capable of maintaining vertical alignment with respect to every other sheet material mounting device comprised by the window covering system. Moreover, there is provided an apparatus and method for adjusting and re-aligning assembled components of a sheet material gripping apparatus.